基于功能化石墨烯液晶的残留偶极耦合定向介质及其应用

Residual dipolar couplings (RDC) have recently become increasingly important in the structural analysis of small organic molecules due to their unique structural information content. However, the application of RDC analysis to small molecules is not yet as widespread as it is for bio-macromolecules. One main limitation for the use of RDC in organic compounds is the orientation that needs to be induced to be able to measure RDC. So far, there are very few alignment media compatible with organic solvents. To address this subject, we wondered whether functional grapheme oxide (fGO) liquid crystals would allow for the orientation of organic compounds and the discrimination of enantiomers. Thus, we will search for a member of a new class of fGO bearing a variety of the side chains due to the slight difference in the alkyl length and polarity induces significant changes in the degree of partial orientation, also develop polymer brushes graft to GO structure to achieve high solubility, low intrinsic viscosity by free radical polymerization, and also develop helical polymer-grafted GO, which induced by amino acids moiety capable of forming chiral liquid crystalline phases for enantiodifferentiating. The liquid crystalline phase can be observed at lower concentrations and the completeness of the phase transition will be judged from the 2H NMR signals. Then, we will get these kinds of fGO lyotropic liquid crystals (LLCs) that are expected to be characterized by low critical concentrations, a low induced degree of order and broad solvent compatibly for the compound in question and enantiodifferentiating properties. Furthermore, Strychnine, Camphor, Menthol, Proline and Isopinocampheol will be selected as analytes to study the alignment properties of the LLCs. These RDCs will be extracted by using various NMR pulses such as J-resolved, E-COSY, CLIP-HSQC, SJS-HSQC and back calculated by using the program package Mspin. The successful method of the structural analysis allows us to extend the applications to some unsolved structures. In addition, the enantiodifferentiating properties of the LLCs also allow us to measure the enantiomeric compositions of chiral organic compounds such as chiral diols by NMR spectroscopy..In a word, this ongoing study will enrich the alignment media and play an important role in expanding the applications of RDC analysis for organic molecules and have significant values in theory and application.

核磁共振残留偶极耦合（RDC）能提供独特的结构信息，在立体结构分析中具有重要作用。然而，由于仅有少数与有机溶剂相溶的定向介质用来提取RDC，其在有机分子中的应用远不如在生物大分子中广泛。本项目拟通过合成不同基团改性的，能与各种有机溶剂形成溶致液晶的功能化石墨烯。以2H(氘核) NMR检测形成溶致液晶的最低浓度和评价定向排列能力，以期获得溶剂范围宽，分析底物广，浓度低，定向角度可控的溶致液晶定向介质。然后，以Strychnine和Isopinocampheol等模式分子为分析对象，通过CLIP-HSQC等技术检测RDC,并以Mspin软件计算，建立有机分子立体化学分析方法。继而开展对难于确定立体结构的天然有机分子解析及测定手性化合物过量值(ee)分析应用研究工作。本项目的实施将丰富有机分子RDC提取介质并扩充液晶NMR技术，拓展RDC在有机结构分析中的应用，具有较大的理论与应用价值。

核磁共振残留偶极耦合参数由于蕴含着独特的空间信息，在有机分子的构型分析中日益地呈现重要性。但是，缺乏检测的分析定向介质，其应用受到了严重的限制。本项目拟通过自由基聚合反应，将分子刷嫁接到氧化石墨烯表面，使其与有机溶剂DMSO兼容，并通过IR，SEM，2H，2D SAXS等技术的表征确认。其形成液晶的定向能力与石墨烯片大小以及浓度相关。通过BOC-色氨酸、雌酮，二氢青蒿素三个模式分子的检测，发现该液晶具有无背景峰，能兼容芳香环化合物，定向角度可控，且简单通过调整浓度来调控强度等优点，且测定精确高。已经被用于药物17-α-ethinylestradiol的构象分析和天然产物新骨架大环内酯环肽dysoxylactam A 的相对构型确定。进一步探索弱极性和中等极性兼容的液晶定向，我们发现了两个液晶定向介质。尤其是甲醇中的液晶定向介质，已被用于若干个复杂天然产物的构象确定。在手性识别研究中，发现功能化的氧化石墨烯没有显示出手性识别作用，但发展了若干核磁共振手性溶剂化试剂。在德国应用化学，JACS，欧洲化学，Organic Letters, Chem. Commun.等期刊上发表系列成果，培养学生6名，撰写了两篇综述，并在多个全国学术会议上交流汇报工作。这个项目的开展，推动和加速核磁共振残留偶极耦合参数在中国的应用并推进这个领域的研究进程。